Some tips from the EFF (https://ssd.eff.org/en/module/attending-protest).
Before the Protest
- Enable full-disk encryption on your device
- Remove fingerprint unlock and FaceID
- Install Signal
- Back up your data
- Buy a prepaid, disposable phone
- Consider biking or walking to the protest (to avoid Automated License Plate Reader Systems)
During the Protest
- Take photos and videos without unlocking your device
- Enable airplane mode
After the Protest
- Scrub metadata on photos
Bridgify may be a good app to have pre-installed also before going to a protest. It’s Bluetooth/peer-to-peer based with mesh network capabilities so you can still message friends (within ~300 feet) if your mobile network is too congested or offline.
Used in Hong Kong protests: https://www.bbc.com/news/technology-49565587
Personal instance of nitrohorse (nitrohorse.com).